Does this filter drop straight into my factory airbox?

Yes. This is a direct replacement for OEM fitment — no adapter, no relocation kit, just swap the old one out and drop this in.

How often should I replace this filter?

Follow your vehicle's service manual interval. Most BMW models call for replacement every 15,000–30,000 miles depending on driving conditions. The red finish makes it easy to spot dirt buildup and know when you're due.

What's the difference between this and a washable filter?

This is a disposable paper-panel design — replace it rather than clean it. Paper filters trap finer particles, which is why BMW engineered them into the factory airbox in the first place.